Optical system for condensing light



I',Aug.3,19ze.' f 1,594,936

v C. H. FRAMPTON OPTICAL SYSTEM FOR CONDENSNG LIGHT I Filed` OCT.. 18,1922 Ulli il Patented ug. 3, 1926.

UNITED 's'rri'rllaisv CHARLES HENRY FRAMPTON, LONDON, ENGLAND.

OPTICAL SYSTEM FORCONDENSING LIGHT.

I Application med October 18, 1922, Serial No. 595,278, and in GreatBritain October 18, 1921.

This invention relates to an optical illuminating system for use inconjunction with cinema projection apparatus and has ,for its object tolutilize the rays proceeding from a given luminous point \to illuminatethe film at the gate of the projection apparatus, and to throw afilm-image on a screen, in place of utilizing the existing open are lampnow universally employed.

In accordance with the present invention the beam of light remainingafter the divergent pencils of rays emitted from the source ofillumination have been reflected byan ellipsoidal reflector` or the likethe exterior or interior surface of which has been silvered or treatedin any manner to convert it into a mirror or reflector, passes .throughsuitable lenses so as to complete the process of concentrating andrenderingl substantially parallel the rays of light be- I fore theselatter pass through the film or slideof the projector. The ellipsoid orhood can be made of any material 'which will serve the required purposeas above set 25 forth.

@ne form of the improved apparatus is shown in axial section in theaccompanying drawing and is adapted to be substituted for the usualexisting open arc and lamphouse and is placed in position behind theprojector in any practical manner.

The optical combination is encased ina metal box in two parts f and gwhich close together by the cylindrical half f being fastened to theconical half g.

In the rear end of the cylindrical part' of vthe box f-is placed theellipsoidal reflector or hood a which is held in position' by thecombined holdero, g, r, w and the T ring z..

The ellipsoidy a is bored or drilled at the apex' to allow the passageof the holder o, q, 7', v through the said aperture. The

shoulder 1' of the threaded tube g on whichv `the hood rests is securedby the gentle pressure ofthe screw collar o. The tube g is then assedthrough the top of the box f and '1s firmly held in position by theknurled screw collar m.

r Through the centre of the combined holder 0, g, r, a: passes the lampholder and wires vof the luminant, which may be retained in the correctposition by any practical method.

In order to remove all strain yfrom the ellipsoid which might be causedby the said holder, and to give greater strength to the box f, the lTring hhas ben introduced.

b indicates the correct position for the luminant, it being importantthat it shouldI occupy a position corresponding with the i passingthrough the second condenser 02, di

rected to an imaginary point, termed the point of common fusion. Therefiected rays vi'zz-p, p, p, p after passing through the minus lens (ilfollow a natural course through an aperture e made in the centre of thesecond condenser 02 alsoto the point of common fusion. The condenser asabove set forth may be replaced by any similar condenser of suitablepower. j

In the centre of therfirst condenser is placed or worked a minus lens orlens-combination d1 which may be worked or placed I in any practicalmanner in relative position `to a simple single condenser if the latteris preferably employed.

The aperture worked or bored in the centre of condenser 02 must be ofequal diameter to that of the minus lens d1.

The final means of producing the desired beam of parallel rays for theprojection of films or slides, already set forth, is, in the exampleillustrated, performed by the in troduction of a minus lens or lenscombmad tion placed within the pointof common fusion. Whether forparallel or slightly convergent light, the diameter of the `beamproduced should not be more than equal to the diagonal of the gate ofthe projector.

The condensed parallelY beam passes out of the optical system throughthe short collar or lens carrier t, and is then directed to the lm.

The condensers c, and e2' which are mounted in the base of the metalcone g j are separated by the ring lc andare secured in permanent vosition by the counter cell lv, into which atter is fitted thecylindrical box f, after having been re-inforced by the ring j.

- m, fm, `indicates a strengthening ring for the base of the conicalpart of the box g.

This invention is intended for use in conjunction with cinema projectionapparatus or any apparatus used or employed for the purpose ofvprojection Aof films or slides, moving or stationary, on to a screen.

By the employment of this inventionheat is reduced suiiiciently topreventcombustion of the film while held stationary at the gate of theprojector for the purpose of examination or demonstration of thefilmimage thrown on to the screen.

The apparatus herein described may be constructed to any size providedthe principal points bear the same relative distances between oneanother, notably the position of the source of illumination (which is atthe first conjugate focal point), 'the second conjugate focal point,hereinbefore referred to, as the first point of concentration and thepoint of common fusion. -It is also imperative that'the curve of theellipsoid be such that all incident light thereon will be truthfullyrelected to the second conjugate focal point.

The optical illuminating system shown is a general construction for thepurpose of utilizing practically the entire illuminating energy of thesource of light, it being po'ssible to pick up and control all theencils of rays except those radiating imme iately behind the saidsource.

I claim:

1. Optical apparatus for projecting, as a substantially parallel beam,virtually' the` whole of therays issuing from a radiant source of li ht,comprising an elli sidal reflector at te rear conjugate foca pointI ofwhich said source of light is' placed, and

rear and frontJ refracting systems, of which the former consists in thecombination with a central refracting element of an annular refractingelement surrounding said central element and the other occupies aposition in front of such combined central and annular j refractingsystem the rays which they respectively receive, and the front refractinsystem is of such character and so place relativel to the virtual pointof common fusiony o the rays proceeding from the combined central andannular refractiluvJ system, as to be adapted to project in su stantialparallelism the rays of light which fall upon it.

2. Optical apparatus as claimed in claim 1, wherein the center of thecombined central and annular refracting system is placed approximatelyat the virtual front conjugate focal point of the ellipsoidal reflectingsurface, said combined refracting system being adapted as a whole todirect to a point of common fusion. all the rays of light which fallupon it.

3. Optical apparatus as claimed in claim 1, wherein the center of thecombined central and annular refracting system is placed in rear of thevirtual front conjugate focal point lof the ellipsoidal reflectingsurface, said combined refracting system being adapted as a whole todirect to a point of common fusion all the rays of light which fall u onit.

4. ptical apparatus as claimed in claim 1, wherein the combined centraland annular refracting system comprises a condenser the central portionof which possesses a negative refractive power.

5. Optical apparatus as claimed in claim 1, wherein the combined centraland annular refracting system comprises two condensers placed the one infront of the other, one of said condensers having a central portionwhich possesses a negative refractive power Iwhile the other has at itscenter a clear aperture.

6. Optical apparatus as claimed in claim 1, wherein the combined centraland"`annular refracting system .comprises two condensers placed the onein front of the other, the central portion of the rear condenser beingconstituted by a minus lens fitted into an aperture therein, while thefront condenser has at its center a clear aperture to give pasage to therays projected by said minus ens.

7. Optical apparatus for projecting, asa substantially parallel beam,"virtually the whole of the rays issuing from a radiant source of light,comprising a concave ellipsoidal reflector adapted to carry the radiantsource at its rear conjugate focal point; a rear refracting systemwhereof the center is placed approximately at the virtual frontconjugate focal point of said reflector, and which consists in thecombination of a condenser placed in front ofthe refiector and havin acentral aperture, a minus lens fittedin said central aperture, and asecond condenser laced in front of the first-mentioned con enser andcentrally apertured to give passage to the rays projected by said minuslens'and a front refractin system; the ellipsoidal reflector being a ated to collect and throw upon the minus ens the greater part of the raysof light issuing from the radiant source, the two condensers and soplaced relatively to saidl point of being adapted to collect virtuallythe Whole common fusion as to be adapted to project remaining portion osaid rays, and the rear in substantial parellelism the rays of light l@refracting system as a Whole being' adapted thrown upon it by tlie rearrerateting sys- 5 to direct to a point of common fusion the tem.

rays of light which fall upon it., While the front reflecting system isof such character CHARLES HENRY FRAMPTN.

